You have been busy today then, glad you got the majority of the wires sorted out.
I have aftermarket reversing sensors & the main unit is fitted behind the rear O/S light cluster & beeper is fitted behind the bulkhead.
Have a good day tomorrow
Least yours isn't a crew cab i have 1 thick black wire running from battery to rear & can only think it's for the tow bar, can't trace it fully as ply is in the way - Hey ho.
Hope it goes well today & the rain stays away for you.